There has been an increasing demand for fire barrier products for use in mattresses and upholstered furniture. Indeed, the U.S. federal open-flame mattress standard (CPSC 16 CFR Part 1633) has created a new demand for flame retardant (FR) fibers in the mattress industry. A number of companies have been developing nonwoven fire barriers to meet the federal standard. Examples of the approaches are described in the following issued patents.
U.S. Pat. No. 7,410,920 (Davis) describes a nonwoven fire barrier consisting of charring-modified viscose fibers (Visil®) with less than 5% of polymers made from halogenated monomers.
U.S. Pat. No. 7,259,117 (Mater et al.) discloses a nonwoven high-loft fire barrier for mattresses and upholstered furniture. The high-loft nonwoven is composed of melamine fiber alone or in conjunction with other fibers.
There are a number of synthetic FR fibers, i.e., the polymer backbone is modified to give flame retardancy. Synthetic FR fibers include aramids (Nomex® and Kevlar®), polyimide fibers (Ultem® polyetherimide and Extem® amorphous thermoplastic polyimide fibers), melamine fiber (Basofil®), halogen-containing fibers (Saran® fiber, modacrylics), polyphenylene sulfide fibers (Diofort®), oxidized polyacrylonitrile fibers (Pyron®), and cured phenol-aldehyde fibers (Kynol® novoloid fiber).
Despite their advantages, these synthetic FR fibers are expensive. From an economic perspective, most of them are not suitable for mattresses and upholstered furniture due to their high costs. For the mattress and upholstered furniture industries, the most cost-effective FR fibers are FR cellulosic fibers.
There are generally two types of FR cellulosic fibers. The first one is FR-treated cellulosic fiber. This is produced by applying FR chemicals on cellulosic fiber. Examples of cellulosic fiber include cotton, kapok, flax, ramie, kenaf, abaca, coir, hemp, jute, sisal, pineapple fiber, rayon, lyocell, bamboo fiber, Tencel®, and Modal®. FR-treated cellulosic fibers are commercially available from Tintoria Piana US, Inc. (Cartersville, Ga., USA).
The second type of FR cellulosic fiber is an inherent FR cellulosic fiber. This is produced by adding FR chemical or FR compound to viscose dope and extruding the dope to form the fiber. Examples of inherent FR cellulosic fiber include phosphorous FR-containing rayon fibers (Lenzing FR®, Shangdong Helon's Anti-frayon®), and silica-containing rayon fibers (Visil®, Daiwabo's FR Corona®fibers, Sniace's FR fiber, and Shangdong Helon's Anti-fcell®).
The most commonly used fire barrier nonwovens for the mattress industry are inherent FR rayon fiber/binder fiber and FR-treated cellulosic fiber/binder fiber. The amount of the binder fiber is typically around 15˜30% of the total nonwoven weight.
Although FR cellulosic fibers provide economical fiber barrier nonwoven for mattresses, there is always industry demand for more economical solutions without sacrificing the fire barrier performance.